1. Field of the Invention
The present invention relates to an optical recording medium which can optically write and read information with the formation of pits by using a beam of light.
2. Related Background Art
Conventionally known optical recording media are those of the type wherein pits (holes) are produced, the type bubbles are formed and the type wherein phase transformation is caused, by irradiation with a beam of light, for example, a laser beam.
Of these, those of the type wherein pits (holes) are formed are constructed by providing on a substrate a thin film comprising a low melting metal such as Te, Bi, Sn, Sb and In, or a dye or pigment (organic coloring matter) of a cyanine type, a squarium type, a phthalocyanine type, a tetradehydrocholine type, a methine type, a naphthoquinone type, a benzene dithiol nickel complex, etc.; or a thin film comprising a composite system of any of these organic coloring matters and metals.
These thin films are irradiated with a beam of light, which is converted to heat energy according to their absorbance, and a recording pit is formed by the heat mode.
The recording pit thus formed is accompanied with bulging-out at the peripheral portion of a recording pit 15 as shown in FIG. 3 to produce a protuberance called a rim 16.
This rim may occur in the process of the melting and solidifying of an optical recording medium, which process is so greatly complicated that the shape and size of the rim can not always be uniform, and thus there have been brought about a disadvantage that may result in the error of a reading signal in reading.